1. Field of the Invention
The present invention relates to multilayer printed circuit boards.
2. Description of the Prior Art
It has previously been proposed to provide circuit boards which carry a pattern of conductors and on to which components may be assembled, the pattern of conductors forming the wiring of a circuit or circuits of which the assembled components form the operative elements. As such circuit boards have developed, so have the available components and the boards are usually now produced by the use of printed circuit techniques. The necessity for quite complex circuit wiring has led to the development of multilayer circuit boards in which wiring patterns are distributed over two or more levels within the thickness of the board. Such multilayer boards are frequently formed by laminating several discrete layers and it is common to provide, as one or more of the inner layers of such boards, electrically conductive sheets frequently termed planes, which are supplied with electrical power and used to distribute the electrical power supplies throughout the board. Such layers, which also serve as screens within the board, are frequently referred to as power supply planes.